Due to excellent mechanical properties (e.g., elongation at break, tear strength, tensile strength, flex life, and abrasion resistance), polymeric compositions based on copolyetherester elastomers have been used in a wide range of applications including manufacture of articles for use in the automotive, wire and cable, fluid power, electrical/electronic, hose and tubing, and appliance fields.
In particular, copolyetherester elastomers are used in the manufacture of insulating layers for wire and cable applications in the automotive, building and construction industries. The wire and cable coating provides electrical insulation but also imparts mechanical, chemical and physical protection. Because temperatures in excess of 125° C. are often reached in the underhood compartments of automobiles or within buildings, temperature specifications for wire and cable insulation materials in both dry and humid environment conditions are constantly increasing. Further, in these highly demanding applications it is necessary that the insulation material meet additional requirements including flame retardancy, thermal resistance, hydrolysis resistance and high elongation.
Polyvinyl chloride (PVC) is the most widely used material for wire and cable insulation. However, in many instances, PVC is perceived as an environmental threat. It would be desirable to have an alternative halogen-free flame retardant thermoplastic material available for use in wire and cable applications that require a flexible material that exhibits resistance to high temperature and hydrolysis as an alternative wire and cable insulation material.
Various flame retardant systems have been developed and used in polymeric material, e.g., polyesters, to improve the fire-resistance thereof. However, due to toxicity concerns, halogen-free flame retardants are gaining increased attention. Among the various halogen-free flame retardants, phosphorus compounds (such as salts of phosphinic or diphosphinic acids) are used extensively due to their stability and flame retardant effectiveness. Prior art has also demonstrated that various types of synergistic compounds can be used in combination with the phosphorus compounds to further maximize the flame retardant effectiveness thereof. For example, U.S. Pat. No. 6,547,992 discloses the use of synthetic inorganic compounds such as oxygen compounds of silicon, magnesium compounds, metal carbonates of metals of the second main group of the periodic table, red phosphorus, zinc compounds, aluminum compounds, or combinations thereof as flame retardant synergists; U.S. Pat. No. 6,716,899 discloses the use of organic phosphorus-containing compounds as flame retardant synergists; U.S. Pat. No. 6,365,071 discloses the use of nitrogen-containing compounds (e.g., melamine cyanurate, melamine phosphate, melamine pyrophosphate, or melamine diborate) as flame retardant synergists; and U.S. Pat. No. 6,255,371 discloses the use of reaction products of phosphoric acids with melamine or condensed product of melamine (e.g., melamine polyphosphate (MPP)) as flame retardant synergists. Moreover, U.S. Patent Publication No. 2008/0039571 discloses the use of metal hydroxides, antimony compounds, boron compounds, phosphorous compounds (e.g., organic phosphate esters, phosphates, halogenated phosphorus compounds, inorganic phosphorus containing salts, etc.), or other metal compounds as primary flame retardants or flame retardant synergists.
Particularly, European Patent Publication No. EP1883081 and PCT Patent Publication Nos. WO2009/047353 and WO2010/094560 each disclose flame retardant elastomeric compositions useful in forming insulating layers and/or jackets of wires and cables. In those disclosures, combinations of (i) a metal salt of a phosphinic acid and/or a diphosphinic acid, (ii) a nitrogen containing compound (e.g., melamine polyphosphate), and (iii) an inorganic compound (e.g., zinc borate) are taught as preferred flame retardant packages. It has been known in the art that the presence of high levels of additives, such as flame retardant additives, in polymer compositions may cause deterioration of certain properties. It is desirable that such polymer compositions have low flammability, high thermal stability and good electrical insulation properties while still maintaining other mechanical properties.
It is an object of the present invention to provide compositions and wires and cables made thereof that exhibit good mechanical performance, good flame retardance and good electrical insulation resistance under dry as well as hot and humid conditions.